Soft Sensor Fabrication Using Rapid Prototype Techniques with Applications in Prosthetic Devices
Touch has been shown to play an important role in proper growth and development across several species. For humans in particular, touch is also instrumental in psychological interaction. The intense complexity of human skin provides additional sensing information key to proprioception. When humans lose proprioception through means of limb loss, they face significant challenges in activities of daily living. Soft robotics, in part, aims to bridge the gap between prosthetic devices and the lack of sensing feedback in traditional devices. Such characteristics are aimed at mimicking the properties and capabilities of the human body. Soft robotics has applications in both therapeutic instances and human-robot interactions. The ever-advancing range of motion achieved by soft robots must be accompanied by equally compliant soft sensors. Current fabrication of liquid embedded elastomeric sensors is commonly accomplished by means of casting, bonding, and manual injection of the metal alloy eGaIn under high-powered microscopy. EGaIn is a non-toxic gallium indium alloy, which is liquid at room temperature and exhibits a density of 6.2 g/cm3. Mass fabrication in the traditional manner is both time consuming and cost prohibitive. With the advent of rapid prototyping, many fabrication processes have shifted toward automated production. Current literature suggests that eGaIn can successfully be used as a material in rapid prototyping. The aim of this research is to directly print eGaIn wires into a soft sensor configuration through means of rapid prototyping, thus fast tracking mass fabrication of liquid embedded elastomeric sensors. EnvisionTech's 3D-Bioplotter, a leader in the field of bioprinting, is used in fabrication trials. Commercially available clear silicone with a durometer reading of 20 Shore A, ultimate tensile strength 213 psi, and ultimate elongation of 347% was used to surround the eGaIn and provide structural support. While the goal of achieving a fully printed soft sensor was not accomplished, several key observations were made during the fabrication process that may aid future research.